Throughout the second half of
"The Fosters" Season 1, Teri Polo's Stef dealt with the aftermath of the shooting at Jesus and Mariana's birth mother's house. Now, during Season 2, she'll also deal with the fallout from another incident with Anna.

"Anna was around and all of a sudden Anna is not around," Polo tells
Zap2it on a May visit to the show's Los Angeles set. "There's some circumstantial evidence that Mike kind of has a bit of a relapse in a fit of anger and Stef becomes a little concerned and a little suspicious that Mike might have had something to do with [Anna's] demise, and so she spends a good deal of the beginning part of the second season investigating that and seeing what the deal is. Alcoholism is a nasty disease."

There's also the fact that Stef's new wife, Lena, is pregnant with a child from a donor who decided to back out on the whole deal, her eldest son, promising concert pianist Brandon, had his hand crushed in an accident, daughter Mariana is going through an identity crisis, and Stef and Lena still can't adopt Callie.

As far as Callie and her paternal drama goes, "I think Stef and Lena are cautiously optimistic that it's going to work out [with Callie's birth father]," Polo says. "They love this girl and they're bound determined that they're going to adopt this girl. It wreaks a little havoc on Jude, quite honestly -- he has a really tough time finding this out and it kind of breaks his little heart. Callie, of course, always struggles with letting anyone in. In the beginning we all view him as a bad guy. How could you abandon your daughter? But we have to find out what the deal here is and what his intentions are."

And for Brandon, "He is dealing with the fact that this injury to his hand could actually be forever and if he did try and have this particular operation it could end up making things worse," Polo says. "He has to decide whether he wants to do it or not and it's a big decision for him. He's got a lot weighing on his heart and soul right now."

Mariana, on the other hand, is just dealing with some good old fashioned teenage identity issues. "Mariana is trying her darndest to fit in, to figure out who she is, to have people like her," Polo says. "She's that poor teenager that struggled in high school and to be popular or to be accepted and she tries everything and ends up getting herself into a lot of trouble and God, if she could just find a boyfriend that stuck around!"

Polo continues, "She's funny and heartrending and so endearing. Mariana's one of our most relatable characters in this sense of what she's going through as a young woman with the added weight of not being raised in a Latino family and trying to figure out, you know, 'Do I care about my roots? Are these important to me? Does it define me? Does it not define who I am?'"